The present invention generally relates to an apparatus for periodically monitoring the composition of a plurality of samples and, in particular, relates to such an apparatus having stationary sample vials and means for selectively withdrawing sample fluid from the stationary vials.
One of the most demanding aspects of many processes, especially manufacturing processes is the need to accurately determine the composition of a fluid, or a group of fluids, at any given time. Such information is demanded not only in instances where the maintenance of a constant composition is critical, but also in instances where the change, with respect to time for example, of the composition is critical as well. Some of the better known of these latter processes is dissolution analysis of pharmaceuticals; fermentation studies; waste product elements analysis; (such as from sewage treatment plants); and environmental studies.
The dissolution analysis of pharmaceuticals is particularly important not only to protect the general public but also to comply with government regulations. This analysis is performed to ensure proper dosage uniformity. In recent times such an analysis has increased in importance and complexity due to the continuing development of multi-active ingredient medicines as well as the increased use of "time-released" medicines.
Presently, the apparatus required for such dissolution analysis studies is expensive, requires excessive volumes of samples due to the loss of sample during analysis and is frequently inaccurate due to cross-contamination of samples.
The conventional apparatus is expensive because of the required fluid conduit systems necessary to supply sequential samples to a translating sample container used during analyses. Presently, most such analyses are carried out using ultraviolet or fluoresence spectrophotometry. This requires a rather complex sample delivery system and is amenable only to single component analysis.
Further, since the sample solution, for example, one in which a tablet is dissolving, is continually reduced the results do not represent the true time dissolution in a specific volume. Hence, the measured dosage dissolved is, in fact, inaccurate.
Finally, because of the rather complex pumping and valving system required, cross-contamination between samples is a frequent occurence. Such cross-contamination results in inaccuracies in the characterizing of samples. This is a particularly acute problem for a multi-active ingredient medication.